1. Field of the Invention
The invention relates generally to a method of forming a metal line in a semiconductor device. More particularly, the present invention relates to a method of forming a metal line in a semiconductor device and forming a selective copper line.
2. Description of the Prior Art
In manufacturing a semiconductor device, a thin copper film can improve the reliability of the semiconductor device due to its higher melting point compared with aluminum and can increase the signal transfer speed because of its low resistivity. Thus, the technology of forming a thin copper film is a technology useful in higher-speed devices and higher-integration devices.
The current method of depositing a thin copper film employs an electro-plating method. The electro-plating method, however, increases the process cost and is sensitive to the process of depositing a seed layer due to its complicated chemical properties. Therefore, it is difficult to establish an optimal condition suitable for the electro-plating method. In the electro-plating method, copper ions are moved by an electric field flowing along the seed layer, thus forming a copper film. If the seed layer is not uniform, a potential drop is generated causing a non-uniform electrolytic layer. Thus, there is a problem that the non-uniform electrolytic layer causes via and voids in the trench structure, thus degrading the characteristics of the copper line.
The present invention to provides a method of forming a metal line in a semiconductor device capable of forming a copper line without forming a seed layer.
In order to accomplish this, a method of forming a metal line in a semiconductor device according to the present invention comprises providing a substrate where a damascene pattern is formed in an interlayer insulating film, forming a diffusion barrier layer on the entire structure in which said damascene pattern is formed, depositing a copper precursor on said diffusion barrier layer, changing said copper precursor into a porous copper layer by means of a baking process, performing a hydrogen reduction annealing process and a force filling process to form a copper layer in which said damascene pattern is completely filled on said porous copper layer, and forming a copper line by polishing said copper layer.